Structure and Bonding of the Hexameric Platinum(II) Dichloride, Pt6Cl12 (β-PtCl2)

• Published in: Zeitschrift für anorganische und allgemeine Chemie (1950) 2003-03, Vol.629 (3), p.516-522
• Main Authors: von Schnering, Hans Georg, Chang, Jen-Hui, Peters, Karl, Peters, Eva-Maria, Wagner, Frank R., Grin, Yuri, Thiele, Gerhard
• Format: Article
• Language: English
• Subjects: Crystal structure; Electronic structure; Platinum; Platinum chloride; Pt6Cl12; Structure relationships; β-PtCl2
• ISSN: 0044-2313; 1521-3749
• DOI: 10.1002/zaac.200390084

The crystal structure of Pt6Cl12 (β‐PtCl2) was redetermined ($R \bar 3 m$ ah = 13.126Å, ch = 8.666Å, Z = 3; arh = 8.110Å, α = 108.04°; 367 hkl, R = 0.032). As has been shown earlier, the structure is in principle a hierarchical variant of the cubic structure type of tungsten (bcc), which atoms are replaced by the hexameric Pt6Cl12 molecules. Due to the 60° rotation of the cuboctahedral clusters about one of the trigonal axes, the symmetry is reduced from $Im \bar 3 m$ to $R \bar 3 m$ ($I \bar 3 m$). The molecule Pt6Cl12 shows the (trigonally elongated) structure of the classic M6X12 cluster compounds with (distorted) square‐planar PtCl4 fragments, however without metal‐metal bonds. The Pt atoms are shifted outside the Cl12 cuboctahedron by Δ = +0.046Å ($\bar {\rm d}$(Pt—Cl) = 2.315Å; $\bar {\rm d}$(Pt—Pt) = 3.339Å). The scalar relativistic DFT calculations results in the full $m \bar 3 m$ symmetry for the optimized structure of the isolated molecule with d(Pt—Cl) = 2.381Å, d(Pt—Pt) = 3.468Å and Δ = +0.072Å. The electron distribution of the Pt‐Pt antibonding HOMO exhibits an outwards‐directed asymmetry perpendicular to the PtCl4 fragments, that plays the decisive role for the cluster packing in the crystal. A comparative study of the Electron Localization Function with the hypothetical trans‐(Nb2Zr4)Cl12 molecule shows the distinct differences between Pt6Cl12 and clusters with metal‐metal bonding. Due to the characteristic electronic structure, the crystal structure of Pt6Cl12 in space group $R \bar 3 m$ is an optimal one, which results from comparison with rhombohedral Zr6I12 and a cubic bcc arrangement. Struktur und Bindung des hexameren Platin(II)‐Dichlorids, Pt6Cl12 (β‐PtCl2) Die Kristallstruktur von Pt6Cl12 (β‐PtCl2) wurde neu bestimmt ($R \bar 3 m$ ah = 13.126Å, ch = 8.666Å, Z = 3; arh = 8.110Å, α = 108.04°; 367 hkl, R = 0.032). Wie schon früher gezeigt, ist die Struktur im Prinzip eine hierarchische Variante des kubischen Wolframtyps (bcc), dessen Atome durch die hexameren Pt6Cl12‐Moleküle ersetzt sind. Wegen der 60°;‐Drehung der kuboktaedrischen Cluster um eine der trigonalen Achsen ist jedoch die Symmetrie von $Im \bar 3 m$ auf $R \bar 3 m$ ($I \bar 3 m$) reduziert. Das Pt6Cl12‐Molekül zeigt die (trigonal gestreckte) Struktur der klassischen M6X12‐Clusterverbindungen mit (verzerrten) planar‐quadratischen PtCl4‐Fragmenten, jedoch ohne Metall‐Metall‐Bindungen. Die Pt‐Atome liegen um Δ = +0.046Å außerhalb der Cl12‐Kuboktaeder ($\bar {\rm d}$(Pt—Cl) =